Transsexualism in a European context The value of NIRT in assessing the utility of DSM-IV-TR diagnostic criteria: a multi-site study on Gender Identity Disorder Muirne Paap Baudewijntje Kreukels Peggy Cohen-Kettenis Hertha Richter-Appelt Griet De Cuypere Ira Haraldsen

Warning! The topic is applied (N)IRT… …no formulae/equations!

About me Currently taking PhD at the clinic for Gender Identity Disorder (GID) in Oslo, Rikshospitalet Studied psychology with a major in clinical psychology and minor in statistics

Collaboration Our clinic has a research collaboration with the clinics in Amsterdam, Hamburg and Ghent Goal: standardize diagnostics and gather questionnaire data

Background IRT has been gaining ground in psychiatric research  investigating properties of clinical diagnoses or instruments  DIF analyses

Aim of this study… …is to use the DSM-IV-TR criteria for the diagnosis Gender Identity Disorder (GID) as an example to illustrate how the utility and generality of different aspects of diagnostic criteria for any DSM diagnosis can be investigated, using Nonparametric Item Response Theory (NIRT).

GID Diagnosis: 4 criteria Strong and persistent cross-gender identification Persistent discomfort about one's assigned sex or a sense of inappropriateness in the gender-role of that sex The diagnosis is not made if the individual has a concurrent physical intersex condition Clinically significant distress or impairment in social, occupational, or other important areas of functioning

Criterion A Criterion A:  Stated desire to be the other sex  Frequent passing as the other sex  Desire to live or be treated as other sex  Conviction that he or she has the typical feelings of the other sex

Criterion B Criterion B:  Preoccupation with getting rid of sex characteristics  Belief to be born the wrong sex

Scoring Criteria from DSM were scored 0 or 1 on:  severity  duration  onset  persistance  frequency Item = subcriterion x aspect

Screenshot of scoring sheet

Sample N=214 applicants (mean age = 32.3, SD = 12.2), seen between jan 07 – march 09 42% were biological females ( mean age = 28.4, SD = 10.4) and 58% were biological males (mean age = 35.11, SD = 12.7). 82% were diagnosed with GID (mean age = 32.8, SD = 12.2). FtMs: 90%, MtFs: 77%.

Method Comparing the centers: On item (symptom) level On scale level Done by using Nonparametric Item Response Theory (Mokken-scale analysis) to construct scales and examine items

NIRT Two models: Monotone Homogeneity Model (MHM) Double Monotonicity Model (DMM)

Main research question current project Are there any differences between centers in the way the GID-criteria are used to reach a diagnosis?  Are the symptoms (items) interpreted in the same way in the four centers?  Is the ordering with respect to popularity comparable?

NIRT Some advantages in a clinical setting: 1. Any functional form of the IRF is allowed, as long as it is monotonely nondecreasing  higher chance of good model-data fit 2. Can be used for relatively small data- sets

Results – ’international scale’  When all data was analyzed together, only 1 scale emerged, combining criterion A & B!

Results – per center For three of the four clinics, a one- scale sollution was found, similar to the international one In Amsterdam, a two-scale sollution was found  however, this was not a two-scale sollution congruent with the A and B criteria in the DSM-IV-R!

Results - Amsterdam Scale one: ‘onset’ and ‘duration’ items (‘Amst 1’) Scale two: ‘severity’ and ‘persistence’ items (‘Amst 2’)  Dutch clinicians might have a different conception of GID

Results – IIO in subgroups The rank-order of the items, according to their ’difficulty’, was similar over the four centers With the exception of the ’persistence’ and ’severity’ of ”Conviction that he or she has the typical feelings of the other sex” These were relatively ‘difficult’ items in Gent. To the contrary, in Hamburg the items are relatively ‘easy’

IRF persistence conviction typical feelings of the other sex 1= Gent 2= Hamburg 3= Amsterdam 4=Oslo

Summary With exception of 1 item, all items were used in a similar fashion in the four clinics when reaching a diagnosis (rank-order) Criterion A & B ended up in one scale in our analysis (international scale) For Amsterdam, a two-scale sollution was found  international differences in diagnostic decisions?

Implications GID: we would suggest that the severity and duration of symptoms should be taken into account in the next version of the DSM Generally: we urge more researchers to consider to use NIRT to scrutinize diagnostic criteria (as listed in the DSM)

Current developments At the moment the DSM-V is under development and it is being considered to enhance the DSM by adding a dimensional adjunct to each of the traditional categorical diagnoses in the DSM  IRT! Kraemer HC: DSM categories and dimensions in clinical and research contexts. International Journal of Methods in Psychiatric Research 2007; 16: S8-S15

Thank you! Thank you for your attention! Any questions?